Hydraulic valves to reconfigure hydraulic circuits have been used in the past. These valves typically reconfigure port alignment and in so doing reconfigure a hydraulic circuit to push a piston in opposed direction for a variety of purposes. Typically these valves have a ported internal shuttle that responds to pressure in an actuation line that overcomes a return spring so that the ports in the shuttle align with different housing ports to reconfigure the hydraulic circuit.
In subterranean locations space for control lines to operate tools is at a premium. In the realm of subsurface safety valves operators frequently desire a backup system for hydraulic actuation of the safety valve. One way to do this is to provide redundant control lines so that if an issue develops with a primary control line such as damage or dents from impacts during running in or even worse a line severing there is a backup control system that can be enabled to keep the subsurface safety valve working. The presence of a backup system can prevent the costly removal of the safety valve and the attendant lost production.
U.S. Pat. Nos. 8,360,158B2/7,954,552B2 entitled Overriding a Primary Control Subsystem of a Downhole Tool describes a system to override a primary control subsystem of a down hole tool. These systems incorporate two control systems but they are not independent. The systems are described as a hydraulic loop with a supply line and a return line that can be switched. The preferred embodiment of the present invention incorporates two independent control systems and does not incorporate a hydraulic loop or exhaust to operate the valve. US 20090050333A1 /U.S. Pat. No. 7,878,252B2 entitled Dual Control Line System and Method for Operating Surface Controlled Sub-Surface Safety Valve in a Well describes a system with two control lines to operate one piston. The device necessitates the pressuring of a primary line to open the valve and the pressure relief of a secondary line to close the valve. The preferred embodiment of the present invention does not incorporate a hydraulic loop or exhaust to operate the valve. U.S. Pat. No. 7,347,270B2 entitled Redundant Hydraulic System for Safety Valve describes a redundant hydraulic system for a safety valve that has a mechanism to selectively translate the secondary piston between a first position at which the secondary piston is not responsive to a control stimulus and a second position at which the secondary piston is responsive to the command stimulus. Another mechanism is used to bias the primary piston to move the flow tube. The preferred embodiment of the present invention does not move the primary or secondary pistons between an active or inactive position, but rather uses a switch to deactivate one piston and activate the other. U.S. Pat. No. 4,621,695A entitled Balance Line Hydraulically Operated Well Safety Valve describes a means of negating the effects of hydraulic head on an operating piston by use of a balance line. This valve uses one control line to the top of the piston and is used to operate the piston to open the valve. A second control line runs from the well surface to the bottom of the piston and is used to compensate for the hydraulic head in the first line. The preferred embodiment of the present invention uses a balance line connected to a chamber, which is communicated to the primary control line after the switch is actuated. U.S. Pat. No. 5,310,004A entitled Fail Safe Gas Bias Safety Valve describes a valve that uses a gas chamber to help offset the hydraulic head acting on a piston. The preferred embodiment of the present invention does not rely on a gas pressure to assist the closure of the pistons. U.S. Pat. No. 4,838,355 entitled Dual Hydraulic Safety Valve describes a valve in which a primary piston is connected to a primary control line and the flow tube. The valve has a secondary piston which is connected to the secondary control line and disconnected from the flow tube. There is a means to switch operating systems by disconnecting the first piston from the flow tube and connecting the second piston to the flow tube. The preferred embodiment of the present invention has a primary piston that is connected to the primary hydraulic line and the flow tube. The preferred embodiment of the present invention has a secondary piston that is not connected to the secondary control line but is not prevented from contact with the flow tube. The preferred embodiment of the present invention has two control lines from the wellhead while this patent describes a mechanism that requires three control lines.
In subterranean locations there can be a serious space problem for control lines. When running two redundant control systems from a wellhead to a subterranean tool such as a subsurface safety valve, having to run a third line to actuate the switch valve between the two systems make the installation impractical if not impossible. The present invention addresses this issue with a switch valve that allows one switch from a primary to a secondary control system with no return to the primary system. Further, the valve is configured to have the two main control lines come to it and switch between them without need for an auxiliary line to effect the switchover. Finally, to prevent accidental switching between the control systems which would normally be triggered by simply applying pressure to the secondary line. a safety device is provided so that the application of pressure just once to the secondary control system will not actuate the switch valve inadvertently. Instead, the pressure has to be cyclically applied to the secondary control system several times to ensure that a switch was actually intended. After the predetermined cycles are applied, the switch device then makes the secondary circuit the primary circuit for uninterrupted operation of the safety valve or the subterranean tool being operated. Those skilled in the art will be able to better understand the invention from the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be found in the appended claims.